Collapsible shipping and storage containers are well known in the art. Collapsibility is desirable in order to minimize the space requirements of the container when it is empty and not in use.
Collapsible containers typically include pivotally attached or foldable side or end walls, a base and optionally a roof. Generally, shipping containers are constructed from wood, metal and plastic parts.
Metal containers are durable with high load bearing capacities, but are heavy. A metal container having inwardly folding horizontally hinged side walls is disclosed in U.S. Pat. No. 5,190,179. The container also has end walls that pivot to within the container where they are stored when the container is collapsed. The metal container contains fork lift tines to allow for its movement when collapsed or erected. Other metal containers having similar features are disclosed in U.S. Pat. Nos. 4,577,772; 3,570,698; 4,848,618 and 4,214,669.
A plywood container having foldable side walls and a collapsible design is disclosed in U.S. Pat. No. 5,253,763.
Plastic containers are lighter than metal containers, are generally not as durable and are typically much smaller in size due to a reduced load bearing capacity. As a result, the storage capacity of plastic containers can be limited. For example, a collapsible shipping container made of plastic is described in U.S. Pat. No. 4,630,746. Each part of the container has a “meshed” structure made by injection molding. The container has two opposing side walls that are inwardly foldable along a vertically hinged axis. In contrast, U.S. Pat. No. 3,870,185 teaches a collapsible plastic container having side walls that are inwardly foldable along a horizontally hinged axis. Further plastic containers having a horizontally hinged collapsible side wall or end wall are disclosed in U.S. Pat. Nos. 3,796,342; 5,038,953; 6,726,046; 6,913,161; 7,137,522; 7,175,040 and CA Pat No. 1,333,055. In addition, U.S. Pat App. No. 2006/0237456 teaches that a latch means can be employed to secure the panels of an inwardly folding side wall in a vertical or erect position.
To impart rigidity and strength to plastic components used in containers, the components are often ribbed or open framework structures, in which flanged sections may be arranged perpendicularly to the vertical or load bearing axis (see U.S. Pat. Nos. 3,985,258; 5,474,197 and 6,484,898).
Commonly owned U.S. patent application Ser. No. 11/827,311, describes the use of twinned wall plastic components to impart high structural strength and rigidity to a collapsible storage container, while at the same time minimizing container weight. The container has an integral roof and end walls which fold inwardly along a horizontal axis and serves as a collapsible storage system. Also, elongate concave cutouts are taught which can be used to increase the flexural rigidity of the wall components.
U.S. Pat. No. 6,631,821, describes an open topped knock down bin, which comprises twinned wall (or “double wall”) components. The double wall components consist of a base, two ends walls and two side walls and are preferably composed of rotomolded plastic. Although the knock down bin can be disassembled, it is not strictly speaking collapsible. For example, none of the walls are pivotally attached to the base in such a way as to facilitate rapid collapsing of the bin. Instead, the bin has a network of horizontally and vertically penetrating reinforcing bars to hold the bin corners together and which must be removed prior to deconstructing the bin. Finally, the bin has vented walls and is not weather proof.
U.S. Pat. No. 4,693,386 and CA Pat. No 1,159,379 each describe a collapsible shipping container made out of twin walled rotomolded plastic components. In each case the containers have four side walls and a base but do not have an integral roof structure. All side walls are pivotally attached to the base. Also, the containers are not weather proof.
In light of the above, there remains a need for weatherproof collapsible containers having good load bearing properties and high storage capacity but without the added weight or corrosion problems of metal component parts.